Electrical apparatus



Nov. 19, 1940. A. CROSSLEY ELECTRICAL APPARATUS Filed Aug. 31, 1938Sheets-Sheet l w m 2 M -m r I 4 7 w fl/ W :liim

RECEPTION CHARACTERISTIC OR ANTENNA SYSTEM EFFICIENCY IN K|LOCYCLE5FREQUENCY a W a Y mm ///VA RECEIVER Nov. 19, 1940. A. CROSSLEYELECTRICAL APPARATUS Filed Aug. 51, 1938 2 Sheets-Sheet 2 Jyezz,

07W, ry 9 ne! S & g M m AN? ///A Patented Nov. 19, 1940 PATENT OFFICEELECTRICAL APPARATUS Alfred Crossley, Chicago, Ill.,, assignor to BeldenManufacturing Company, Chicago, 111., a" corporation of IllinoisApplication August 31, 1938, Serial No. 227,604

13 Claims.

My invention relates to the art of radio communication, and has for itsprincipal object the provision of an' improved antenna system for use inconnection with receiving sets adapted to receive signals in amultiplicity of wave bands, as

for example, receiving sets adapted to receive either long or short wavesignals. I

Other objects of my invention are to provide an improved antenna systemfor use with multiple wave band receiving sets which shall include aseparate metallic circuit for conducting the signal energy of each waveband from the antenna to the set; to provide an improved antenna systemfor multiple wave band receiving sets which shall effectively eliminatelocal interference noise during the operation of the set by preventingenergy from local interference sources from reaching the receiving set,while at the same .time transmitting the signal energy from the antennato the receiving set at a very high efliciency; and to provide anantenna system for multiple wave band receiving sets, especiallyreceiving sets adapted to receive either long or short wave signals,which shall have a uniformly high reception characteristic over theentire reception range of the set, i. e., which shall be free from deadspots or bands of impaired reception such as are inherently present inmany of the antenna systems now on the market.

The manner of accomplishing these objects and the various novel featuresand important advantages of my invention will be made more apparent inthe following description of certain embodiments of my invention takenin conjunction with the accompanying drawings. In the drawings Figure 1is a circuit diagram of an antenna system embodying the features of myinvention;

Figure 2 is a curve illustrating the reception characteristics of theantenna system illustrated in Figure 1;

Figure 3 is a fragmentary elevational view illustrating one form ofdownlead conductor suitable for use in the antenna system of Figure 1;

Figure 4 is a fragmentary elevational view similar to Figure 3illustrating a second form of 5 Figure '7 is a circuit diagram, similarto Figure 1, illustrating a modified form of the antenna system of myinvention; and

Figure 8 is a fragmentary elevational view, similar to Figures 3 and 4,of a downlead conductor particularly intended for use in the antennasystemof Figure '7.

While the principles of the present invention are applicable to antennasystems for use in conjunction with receiving sets adapted to receivesignals in more than two wave bands, the principal present use for theinvention is in connection with ordinary home receiving sets which areadapted to receive long wave signals (in the broadcast band) andordinary short wave signals. In View of this, the embodiments of theinvention illustrated in the drawings and described herein compriseantenna systems for use in connection with receiving sets which areadapted to receive signals in two wave bands, particularly therelatively long wave broadcast band and the ordinary short wave band. Itis my intention, however, that this disclosure of an antenna system formerely a two band range in particular portions of the wave spectrumshall not be deemed to limit the invention in any way. Tests have shownthat antenna systems in accordance with my invention may beadvantageously used for more than two wave bands and in practically anyportion of the wave spectrum.

As illustrated diagrammatically in Figure 1, an antenna system inaccordance with my invention comprises a transformer unit 1 adapted tobe located adjacent the antenna 8, a plurality of downlead conductors 9,I0, and H, and a second transformer unit l2 intended to be locatedadjacent the receiving set l3. The transformer units 1 and I! arearranged to cooperate with the antenna 8 and the downlead conductors 9,l0, and II in such manner that a rise or fall in the potential of theantenna with respect to ground due either to long wave broadcast signalsor to short wave signals will produce a corresponding signalingpotential across the antenna and ground terminals of the receiving set,indicated at M and I5, respectively. The signaling potentials due tolong wave length signals are, however, conducted from the antenna to theset over a different circuit than the signaling potentials due to shortWave signals.

By this arrangement I obtain what I prefer to designate as free channelreception. In other words, the signal energy of each band is conductedfrom the antenna to the set by a separate conducting channel. Thearrangement makes for extremely high efliciency in the antenna system,particularly when certain types of very closely coupled transformers areused in the transformer units I and I2. In fact, tests indicate that atleast of the energy impinging upon the antenna can be transmitted to theset by the system of my invention, as compared with maximum transmissionefliclencies of about 32.5% in the systems now used in the art.Moreover, this free channel circuit arrangement malges possible thecomplete elimination of trap circuits in the antenna system which mighttend to produce impaired reception at certain wave lengths, adisadvantage which is to be found in most of the antenna systems of thischaracter now known in the art.

The antenna 8 used in the system of my invention probably may be of anyof, the conventional types, such as a flat-topped L, inverted L, T type,doublet, etc. However, I prefer to use a composite, fiat-topped antennahaving a long branch ll of the L type and a short branch l8, or halfdoublet, the two branches being angularly disposed relative to oneanother, as is illustrated diagrammatically in Figure 1. For ordinaryshort wave and broadcast bands, 1. e., in bands of 4,000 to 22,000kilocycles, and from 400 to 4,000 kilocycles, particularly satisfactoryresults will be obtained with an antenna the longer branch of which isabout 60 ft. long and the shorter branch of which is about 22 ft. inlength, the two branches being connected at one end to form the apex ofan angle of about 30 or 40.

The signal energy is conducted from the antenna to the receiver by asufficient number of downlead conductors to provide a separatecircuit-for the signal energy in each wave band. Thus, for a two bandsystem the minimum number of downlead conductors is three, asillustrated at 9, ill, and l I in the drawings, the downlead l0 beingcommon to both circuits. These downleads may comprise a triplex cable l9consisting of three insulated wires 20 twisted together and enclosed ina protective fabric outer sleeve 2|, as is illustrated in Figure 3; orthree separate conductors insulated from one another; or preferably acable 23 consisting of two insulated wires 24 which are enclosed in asleeve conductor 25 of metal braid, or the like, :as is illustrated inFigure 4. In this last mentioned structure the two insulated wires 24are preferably wound about each other to form a twisted pair, insulation26 is interposed between the wires 24 and the metallicsleeve 25, and aprotective insulating covering 21, which may be waterproof, is placedover the sleeve 25.

Regardless of which of these three types of downlead is used, thedownlead conductor designated as ill in the circuit diagram of Figure 1is permanently connected to ground. If the conducting sleeveconstruction of Figure 4 is used, the sleeve 25 will be employed as thegrounded downlead conductor I0, since the sleeve 25 will then serve toshield the other two downloads 9 and II and effectively preventinterference energy from local sources from being conducted to thereceiving set I3. I

The antenna transformer unit 1 comprises a short wave step downtransformer 29 and a long wave step down transformer 30. One end of theprimary of each of the step down transformers 29 and 30 is permanentlygrounded, as by being connected to the grounded downlead conductor ID at3|. The other end of the primary of the step down long wave transformer301s connected directly to the antenna 8, as by the conductorillustrated at 32, and the other end of the primary of the step downshort wave transformer 29 is connected to the antenna through acondenser, as illustrated at 33.

The electrical constants of the step down transformers 29 and 30 and thecondenser 33 are such as to provide a low impedance path from theantenna to ground for long wave signals through the primary of the longwace transformer 30, and a low impedance path for short wave signalsfrom the antenna to ground through the primary of the short wavetransformer 29,

while at the same time providing a high impedance path for short wavesignals through the primary of the long wave transformers 29 and a highimpedance path for long wave signals through the primary of the shortwave transformer 29.

One end of each of the secondaries of the lon and short wave step downtransformers 29 and 30 is grounded, as by being connected to thegrounded downlead conductor l0 at 34. The other end of the secondary ofthe step down long wave transformer 30 is connected to the downleadconductor 9, and the other end of the secondary of the step down shortwave transformer 29 is connected to the downlead conductor II.

It will be evident that the result of this arrangement is to provide acircuit wherein any change in the potential of the antenna 8 withrespect to ground due to a long wave signal will impress a signalingpotential across the downlead conductor 9 and the grounded downleadconductor I 0. Likewise, any change in the potential of the antenna 8relative to the ground dueto a short wave signal will impress asignaling potential across the other downlead conductor II and thegrounded downlead conductor 10. While the ground lead I 0 is common toboth circuits, an independent channel is provided in the downleadarrangement for both types of signal energy.

The other transformer unit I2 is similar to the antenna transformer unit1 and includes a short wave step up transformer 31 and a long wave stepup transformer 38; one side of the primary of each of the step uptransformers 31 and 38 is grounded, as by being connected to thegrounded downlead ill at 39. The other side of the primary of the longwave step up transformer 38 is connected to the long wave downlead 9,and the other side of the primary of the short wave step up transformer31 is connected to the short wave downlead ll.

One side of the secondary of each of the step up transformers 31 and 38is likewise grounded, as by being connected to the grounded downlead lllat 40. The other side of the secondary of the long wave step uptransformer 38 is directly connected by metallic conductors 4| to theantenna terminal M of the receiver I 3. The other side of the secondaryof the short wave step up transformer 31 is connected to one of theconductors 4| through a condenser 42. The condenser 42 permits theobtaining of an impedance in the short wave side of the set transformerunit I2 which substantially prevents. any circulating of the lowerfrequency, long wave energy, while at the same time the inherently highinductance ofthe secondary of the long wave step up transformer l2effectively prevents any loss of short wave energy by virtue of theshunt relation of the two secondaries.

The individual long and short wave transformers 29, 30, 91, and 99 usedin the transformer units 1 and I2 may be of any conventional type.However, the inherent advantages of the circuit of the present inventionare fully realized only when transformers having the maximum possiblecoupling are used in these units, the minimum permissive limit,consistent with full realization of the advantages of the invention,being about 75% coupling. Because of this characteristic of the system,my invention makes possible, and in fact almost requires, the use ofmetallic core transformers, such as iron dust core transformers, in thetransformer units.

Iron dust transformer cores, as is well known in the art, comprisemixtures of very finely divided, individually insulated particles ofiron dust or magnetic oxide, and a binder which serves to support theindividual particles. These mixtures may be molded into any convenientform, and it is customary to wind the transformer coils directly uponthe core. With a metallic core of this type it is readily possible tosecure couplings in excess of 90% whereas the maximum couplingobtainable with an air core transformer is about 57%, and since theefficiency of energy transfer is a function of the coupling, it will beapparent that the ability of the system of the present invention to useclosely coupled transformers it is a most important feature of theinvention.

A type of closely coupled transformer unit which I have foundparticularly satisfactory in the system of my invention is illustratedin Fi ures 5 and 6. This transformer unit includes a base 45 of suitabledimensions, which may be cut from a sheet of insulating material, and acylindrical core support 46 also of insulating material which serves asa support for the core 41 of the long wave transformer 49 and thesimilar core 49 of the short wave transformer 50. The cores 4! and 49are of the iron dust or magnetic oxide type and preferably have the formillustrated in Figure 6. The transformer windings 5| and 52 preferablycomprise bifllar wound, honeycomb coil units, 1. e., windings whereinthe primary and secondary windings of each transformer are woundsimultaneously in parallel turns, as illustrated in Figure 6, where thefirst turn 53 of a primary winding is shown with shading and the firstturn 54 of the cooperating secondary winding is shown unshaded.

To obtain the maximum coupling in the transformer unit as a whole, thetwo cores 41 and 49 are preferably mounted coaxially upon the support 46and may be held in place by a headed wooden dowel pin 56 and screw 55,as illustrated in Figure 5. This type of transformer unit wh le merelyillustrative is one which has proven particularly satisfactory in actualservice.

In order to obtain maximum efficiency in the system, it is verydesirable that the long and short wave transformers 29, 30, 91, and 38shall be of the matched impedance type. In other words the transformerturns ratio and coupl n should be such that the low impedancetransmission is substantially matched to the antenna and the radioreceiver input circuit.

In a specific embodiment of the invention which gave particularlysatisfactory results, the condensers 33 and 42 had a capacity of 80 m.m. f. The short wave step down transformer 29 of the antenna transformerunit I had a turn primary and a 5 turn secondary, and the associatedlong wave transformer 30 had a primary of 100 turns and a secondary of20 turns. The primary of the short wave step up transformer of the settransformer unit l2 had a 5 turn primary and a 22 turn secondary, andthe primary of the associated long wave step up transformer 28 had a 20turn primary and a 78 turn secondary. Each of the individualtransformers was woundon a molded, oxide dust core having a dimension Ain Figure 6 of about /2". a dimension B of about and a dimension C ofabout /8, A. W. G. #36 enameled wire with one layer of silk insulationused for all windings. The coils were bifilarly wound in honeycomb form.

When the system of the present invention is used for the reception ofvery short wave signal energy, it will be found that a downlead cable ofthe type shown in Figure 4 will have a tendency to pick up certain typesof noise energy due to the natural inductance of the shield providingappreciable coupling impedance at these very high frequencies. However,if the system of Figure 1 is modified as shown in Figure 7 and adownlead conductor 51 having three insulated wires 58 enclosed within abraided conducting sleeve 59, as illustrated in Figure 8, is used thisdifficulty will be'obviated.

The system of Figure 7 is substantially identical with the system ofFigure 1, except in the following respects: One, the secondaries of theantenna unit transformers 29 and 30 and the primaries of the set unittransformers 31 and 38 are ungrounded in the Figure 7 system. Two, thethree downlead conductors 9, l0, and II connecting the secondaries ofthe antenna unit transformer and the primaries of the set unittransformers are likewise ungrounded in .the Figure 7 system. Third, thedownlead conductors 9 Hi and ll of the Figure 7 system are shielded by agrounded conducting sleeve 6| (which will comprise the sleeve 59 if acable such as is illustrated in Figure 8 is used); this sleeve BI isconnected at its upper end to the interconnected primaries of theantenna unit transformers at 3| whereby it serves as the groundconnection for that unit. And, four, the connection between the points39 and 40 of the Figure 1 system is eliminated in the Figure 7 system,the interconnected secondaries of the set unit transformers beingdirectly grounded by a connection 63.

The net result of these differences is merely to provide a groundedshield for the downlead conductors which is insulated from thoseconductors and the transformer windings which they connect. Thisarrangement, while providing a satisfactory path to ground for theprimaries of the antenna unit transformers in order that changes inpotential of the antenna with respect to ground shall providecorresponding changes in the potential across the downleads, serves toprovide a complete shielding of the downlead circuit which prevents pickup of noise or interference energy. Except for this shield and themanner in which it is connected into the circuit, the system of Figure7, as stated previously, is substantially identical with the system ofFigure l and operates in precisely the same manner.

As stated above, tests of the antenna system of my invention have fullyestablished its remarkable efficiency and its freedom from thedisadvantages of the prior art arrangements. Outstanding among theseadvantages is the remarkable electrical emciency of the system whichpermits substantially twice as much of the energy at any particularfrequency incident upon the antenna to be transmitted to the setterminals as was obtainable with previous types of the ratio of energyimpinging upon the antenna to energy delivered by the antenna system tothe receiver over the operative frequency band, i. e., the electricalefficiency of the antenna system.

At the transition point-about 4,000 kilocycles it will be found thatsome of the energy is transmitted to the set from both the long wave andthe short wave sides of the system. Because of this, it is possible toobtain a flat reception characteristic in the region of this frequency.In many of the prior art systems a marked decreased efficiency isencountered in this range.

The important advantages of the system of my invention are believed tobe due to the fact that a separate circuit is provided for conductingthe short wave and long wave energy from the antenna to the set, i. e.,the provision of a free channel for each type of signal. The markedelimination of local interference noise without impairment or reductionof the signal energy is also believed to result in part from this freechannel circuit arrangement since that arrangement particularly lendsitself to complete shielding of the downleads, preferably by the use ofthe conducting sleeve cable constructions dis-.

closed in Figures 4 and 6, although reasonably satisfactory shieldingmay be obtained by the triplex cable construction illustrated in Figure3 because of the presence of grounded conductor l0 and the low impedanceof such conductor.

It will be apparent to those skilled in the art that various types ofantenna systems embodying the principles which I have disclosed in theforegoing may be constructed. For instance, if it should be desired toprovide an antenna system for three or four wave band reception insteadof two wave bands, additional units may obviously be added to the systemdisclosed. It is my intention, therefore, that the accompanying claimsshall be accorded the broadest reasonable construction consistentwiththe language apv pearing therein and the prior art.

I claim the following as my invention:

1. In a radio receiving system; a receiving set for long and short wavesignals; an antenna; an antenna transformer unit comprising a step downtransformer for long wave signals and a step down transformer for shortwave signals; three downlead conductors which are insulated from eachother and are enclosed within a conducting sleeve; said sleeve beinginsulated from said downlead conductors and being permanently connectedto ground; one side of the primary of each of said step downtransformers being connected to said grounded sleeve; the other side ofthe primaries of said step down transformers being electricallyconnected to said antenna; one side of the secondary of both of saidstep down transformers being connected to a single downlead conductor;the other side of the secondary of each of said step down transformersbeing connected respectively to one of the other two downleadconductors; a set transformer unit comprising a step up transformer forlong wave signals and a step up transformer for short wave signals; oneside of the primary of each of said step up transformers being connectedto said first mentioned downlead conductor; the other side of theprimary of said long wave step up transformer being connected to thedownlead from the secondary of the long wave step down transformer, andthe'other side of the primary of said short wave step up transformerbeing connected to the downlead from said short wave step downtransformer; one side of the secondary of said short wave step uptransformer and said long wave step up transformer being grounded, and

the other side of each of said secondaries of said step up transformersbeing electrically connected to said receiver.

2. In a radio receiving system; a receiving set for long and short wavesignals; an antenna; an antenna transformer unit comprising a step downtransformer for long wave signals and a step down transformer for shortwave signals, both transformers being of the matched impedance type;three downlead conductors which are insulated from each other and one ofwhich is permanently grounded; one side of the primary of each of saidstep down transformers and one side of the secondary of each of saidstep down transformers being connected to said grounded downleadconductor, the other side of the primary of said long wave transformerbeing connected directly to said antenna and the other side of theprimary of the short wave transformer being connected to said antennathrough a capacitance, the other side of the secondary of each of saidstep down transformers being connected respectively to one of the twoungrounded downlead conductors; a second transformer unit comprising astep up transformer for long wave signals and a step up transformer forshort wave signals; both transformers being of the matched impedancetype, one side of the primary of each of said step up transformers andone side of the secondary of each of said step up transformers beingconnected to ground, the other side of the primary of said long wavestep up transformer being connected to the downlead from said long wavestep down transformer, and the other side of the primary of said shortwave step up transformer being connected to the downlead from said shortwave step down transformer, the other end of the secondary of said longwave step up transformer being directly connected to the antennaterminal of said receiving set, and the other side of the secondary ofsaid short wave step up transformer being connected to the antennaterminal of said receiving set through a condenser.

3. A radio receiving system for receiving signals in two different wavebands comprising an antenna, means, including three separate downleadconductors, providing a separate, two-conductor, downlead transmissioncircuit from said antenna to the receiving set with which said sys* temis used for each of said wave bands, one of said downlead conductorsbeing common to both of said downlead transmission circuits, and meanswhereby fluctuations in the potential of said antenna with respect toground due to signals in either wave band cause like potentialfluctuations to be set up only in the downlead transmission circuitprovided for that wave band.

4. A radio receiving system for receiving signals in two different wavebands comprising an antenna, means, including three separate downleadconductors, two-conductor, downlead transmission circuit from saidantenna to the receiving set with which said system is used for each of.said wave bands, one of said downlead conductors being permanentlyconnected to ground and being common to both of said downleadtransmission circuits, and means whereby fluctuations in the potential01 said antenna with respect to ground due to signals in either of saidwave bands cause like potential fluctuations to be set up only in thedownlead transmission circuit provided for that we've band.

5. A radio receiving system for receiving signals in two difierent wavebands comprising an antenna, means including a pair of downleadconductors which are enclosed within a conducting sleeve and which areinsulated from each other and from said sleeve, providing a separate,two-conductor, downlead transmission circuit from said antenna to thereceiving set with which said system is used for each of said wavebands, said conducting sleeve being permanently 'connected to ground andconstituting a common conductor of both of said downlead transmissioncircuits, and means whereby fluctuations in the potential of saidantenna with respect to ground due to signals in either of said wavebands causes like potential fluctuations to bet set up only in thedownlead circuit provided for that band.

6. A radio receiving system for receiving signals in two difierent wavebands comprising an antenna, means, including three separate downleadconductors, providing a separate, two-conductor, downlead transmissioncircuit from said antenna to the receiving set with which said system isused for each of said wave bands, one of said downlead conductors beingpermanently connected to ground and being common to both of saiddownlead transmission circuits, and means, including a step-downtransformer having a coupling of at least 75% interposed between theantenna end of each of said downlead transmission circuits and saidantenna and a step-up transformer also having a coupling of at least 75%interposed between the set end of each of said downlead transmissioncircuits and the receiving set with which said system is used, wherebyfluctuations in the potential of said antenna with respect to ground dueto signals in either of said wave bands causes like potentialfluctuations to be set up only in the downlead transmission circuitprovided for that band.

7. A radio receiving system for receiving signals in a plurality ofdifferent wave bands comprising an antenna, means, including threeseparate downlead conductors, providing a separate, low impedance,two-conductor, downlead transmission circuit from said antenna to thereceiving set with which said system is used for each wave band which isto be received, one of said downlead conductors being permanentlyconnected to ground and constituting a common conductor of both of saiddownlead transmission circnits, and means, including a step-downtransformer interposed between the antenna end of each of said downleadtransmission circuits and said antenna and a step-up transformerinterposed between the set end of each of said downlead transmissioncircuits and the receiving set with which said system is used, wherebyfluctuations in the potential of said antenna with respect to ground dueto signals in either of said wave bands causes like potentialfluctuations to be set up only in the downlead transmission circuitprovided for that band.

8. A radio receiving system for receiving signals in two different wavebands comprising an antenna, means, including a pair or downleadconductors whichare enclosed within a conducting sleeve and which areinsulated from each other and from said sleeve, providinga separate, 5two-conductor, downlead transmission circuit from said antenna to thereceiving set with which said system is used for each of said wavebands, said sleeve being permanently connected to ground andconstituting a common conductor of both of said downlead transmissioncircuits, and means, including a step-down transformer having a couplingof at least 75% interposed between the antenna end of each of saiddownlead transmission circuits and said antenna and a step-uptransformer having a coupling of at least 75% interposed between the setend of each 01' said downlead transmission circuits and the receivingset with which said system is used, whereby fluctuations in thepotential of said antenna with respect to ground due to signals ineither of said wave bands causes like potential fluctuations to be setup only in the downlead transmission circuit provided for that band.

9. A radio receiving system for receiving signals in two difierent wavelengths comprising an antenna, means, including three separate downleadconductors, providing a separate, two-conductor, downlead transmissioncircuit'from said antenna to the receiving set with which said system isused for each wave band which is to be received, one of said downleadconductors being common to both of said downlead circuits, and means,including a step-down, iron core transformer interposed between theantenna end or each of said downlead transmission circuits and. saidantenna and a step-up, iron core transformer interposed between the setend of each of said downlead transmission circuits and the receiving setwith which said system is used, whereby fluctuations in the potential orsaid antenna with respect to ground due to signals in either or saidwave Ibands causes like potential fluctuations to be set up only in thedownlead transmission circuit provided for that band.

10. A radio receiving system for receiving signals in a plurality ofdifierent wave lengths comprising an antenna, means, including three,separate, downlead conductors, providing a separate, two-conductor,downlead transmission circuit from said antenna to the receiving setwith which said system is used for each wave band which is to bereceived, one of said downlead conductors being common to both of saiddownlead circuits, means, including a step-up transformer interposedbetween the antenna end of each of said downlead transmission circuitsand said antenna, whereby fluctuations in the potential or said antennawith respect to ground due to signals in any of said wave bands causelike potential fluctuations to be set up only in the circuit providedfor that wave band, and a step-up transformer interposed between the setend of each of said downlead transmission circuits and the receiving setwith which said system is used, the electrical constants of both saidstep-up and said stepdown transformers being such that substantialmatching of impedances is obtained in each of said downlead transmissioncircuits.

11. A radio receiving system for long wave and 7 short wave signalscomprising a flat top, V-type antenna, one of the arms of which is muchlonger than the other, means, including three separate downleadconductors, two-conductor, downlead transmission circuit from saidantenna 75 to the receiving set with which said system is used for eachof the two wave bands which is to .be received, and means wherebyfluctuations in tenna, the two arms of which are of different lengthsand are respectively adapted for the reception of long wave and shortwave electromagnetic energy, means, including three separate downleadconductors, providing a separate, twoconductor, downlead transmissioncircuit from said antenna to the receiving set with which said system isused for each wave band which is to be received, one of said downleadconductors being permanently connected to ground and constituting acommon conductor in both of said downlead transmission circuits, andmeans whereby fluctuations in the potential of said antenna with respectto ground due to signals in either of said wave bands cause likepotential fluctuations to be set up only in the downlead transmissioncircuit tenna, the two arms of which are of different lengths and arerespectively adapted for the reception of long wave and short waveelectromagnetic energy, means, including three separate downleadconductors, providing a separate, twoconductor, downlead transmissioncircuit from said antenna to the receiving set with which said system isused for each wave band ,which is to be received, one oi! said downleadconductors being permanently connected to ground and constituting acommon conductor in both of said downlead transmission circuits, meanswhereby fluctuations in the potential of said antenna with respect toground due to signals in either of said wave bands causeslike potentialfluctuations to be set up only in the downlead transmission circuitprovided for that wave band, said last mentioned means including astep-down, iron core transformer interposed between the antenna end ofeach of said downlead transformer circuits and said antenna, and astep-up, iron core transformer interposed between the set end of each ofsaid downlead transformer circuits and the receiving set with which saidsystem is used, the electrical constants of said transformers being suchthat substantial matching of impedances is obtained in each of saiddownlead circuits.

ALFRED CROssmev CERTIFICATE OF CORRECTION. V Patent No. 2,222,)4D6-November 19, 191m.

ALFRED CROSSLEY.

It is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction asfollowe Page 2, sec-0nd column, line 11, for "wace" re ad --wave--; page 5, first column,line 52, strike out "it"; page 1 second column line 75, and page 5,second column, line 71+, claimsb. and 11 respectively,heforefitwoconduetor" insert the words and comma --providing eseparate,--; page 5, first column, line 27, claim 5, for "bet" read--be--; and that the said Letters Patent should e 'read with thiscorrection therein thqt the same mey conform to the rec- Zrd of the.case in the Patent Office.

Signed and sealed this 28th day of January, A. D. 19131.

Henry Van Arsdeile, (Seal) Acting Cemmissioner of Patents.

